Multimedia Broadcast Multicast Service (MBMS) is a broadcasting technique for E-UTRAN that optimizes downlink radio resource when a large number of users are interested in receiving the same content (e.g., video broadcast). MBMS generally covers a large geographic area that may comprise one or more cells. When the cells distribute the same services, MBMS single frequency network (MBSFN) transmission may increase the spectral efficiency of MBMS transmissions. In MBSFN transmission, identical data is transmitted on the same radio resources from each cell. Cells that offer the same set of MBMS services and the same scheduling of MBMS service sessions belong to one MBSFN area.
A wireless device, which may also be referred to as User Equipment (UE), uses an MBMS control channel (MCCH) to obtain service specific information used for MBMS service reception (e.g., physical multicast channel (PMCH) configuration such as modulation and coding scheme, MBMS subframe allocation, etc.).
MBMS may operate on an MBMS dedicated carrier frequency or on a shared carrier frequency (i.e. shared between MBMS and unicast). In the former case all subframes may be used for MBMS signal transmission. In the latter scenario, MBMS service and unicast service are shared, for example, in a time division multiplex manner (i.e., different subframes within a radio frame are used for MBMS and unicast services). The MBMS subframes may be configurable by the network node. The information regarding which subframes are configured for MBMS in a cell may be signaled by the network node. Examples of subframes that can be configured for MBMS (i.e., as MBSFN subframes) are subframes #1, 2, 3, 6, 7 and 8 for LTE FDD and subframes #3, 4, 7, 8 and 9 for LTE TDD. Subframes #0 and #5 are unicast subframes in both FDD and TDD. In LTE FDD, the subframes #4 and 9 and are also unicast subframes. In LTE TDD, subframes #1, 2 and 6 are also unicast subframes. The unicast subframes are used for unicast services.
An eNodeB (eNB) may be configured with MBMS scheduling information by a network entity referred to as a Multi-cell/Multicast Coordination Entity (MCE). An MCE may be a separate network node or may reside in an eNB. The MCE and eNB communicate over an M2 interface. The M2 interface is a logical interface between the eNB and the MCE.
An MBMS Scheduling Information Procedure provides MCCH related information to the eNBs that take part in the transmission. The procedure uses non MBMS-Service-associated signalling. Specifically, an MCE may initiate the procedure by sending a first message to the eNB that includes MBMS scheduling information. This first message provides MCCH related information to the eNB. For example, the first message may contain information such as MBSFN subframe configuration, common subframe allocation period, MBSFN Area ID, etc. The eNodeB uses this information for creating MBSFN subframe(s) and for creating the contents of the MCCH, which in turn is signalled to the UE over the radio interface. The successful reception of this message may be confirmed by the eNodeB in a response message.
For the scheduling of MBMS to the wireless device, MCCH information may be transmitted periodically and may be transmitted according to a configurable repetition period. Scheduling information may not be provided for MCCH (i.e., both the time domain scheduling as well as the lower layer configuration may be semi-statically configured, as defined within SystemInformationBlockType13 (SIB13)). For example, the SIB13 contains the information to acquire the MBMS control information associated with one or more MBSFN areas. The wireless device may also be provided with SystemInformationBlockType15 (SIB15). The SIB15 contains the MBMS Service Area Identities (SAI) of the current and/or neighbouring carrier frequencies.
For MBMS user data, which is carried by the MTCH logical channel, E-UTRAN periodically provides MCH scheduling information (MSI) at lower layers (e.g., MAC layer). This MCH information concerns the time domain scheduling (i.e., the frequency domain scheduling and the lower layer configuration are semi-statically configured). The periodicity of the MSI is configurable and defined by the MCH scheduling period.
MDT is a feature used for configuring a wireless device (i.e., UE) to log one or more radio measurement results along with associated information. Such information may comprise location information such as a location where the measurement is performed, timing information such as a timestamp when the measurement is performed, or any other information associated with a radio measurement. The wireless device may be configured to log such measurements during a low activity state (e.g., idle state) and/or in RRC Connected state. The wireless device may then report the logged information to the network node when the wireless device goes into the RRC Connected state. The network node uses the MDT related information received from wireless devices for network deployment related functions (e.g., determination of coverage holes, network planning, configuration of system parameters, etc.). The MDT reduces the need for doing drive tests for network planning and optimization.
A network node (e.g. eNodeB) may configure a wireless devices to log measurements performed on MBMS-related signals such as, for example, MBSFN RSRP (on MBSFN reference signals), MBSFN RSRQ (on MBSFN reference signals), and MCH BLER (on MCH). These measurements are configured and performed in MBSFN subframes that transmit MCH. The measurements may be configured per MBSFN area (up to 8 MBSFN areas) and per MCH (up to 15 MCHs within an MBSFN area). The requested measurements may be limited to one or more PLMNs, one or more cells, one or more tracking areas, and/or one or more specific carrier frequencies. The measurements in the measurement logs may be linked to a time stamp and/or positioning information that are available in the wireless device. The time stamp may be expressed in absolute or relative values. The relative time stamp may be defined as the time elapsed from a reference time to the moment the measurement is logged by a radio node. The relative accuracy of the time stamping (i.e., relative time stamp accuracy) is the drift of the time stamping (e.g., ±1 second). It may also be expressed in terms of parts per million (ppm) or parts per billion (ppb) over a certain time duration (e.g., ±200 ppb over 1 hour). This example corresponds to ±0.72 seconds of drift in a time stamp over a period of 1 hour.
Wireless devices may receive logging configuration parameters from an eNB or other network node in a LoggedMeasurementConfiguration messages. Example parameters may include trace reference, trace session and TCE (Trace Collection Entity) information; logging interval; logging duration; time information (absolute time in the current cell); PLMN list; area list; and/or target MBSFN area list.
FIG. 1 is a swim-lane diagram illustrating the interaction of a wireless device 110 and network node 110 for the configuration and performance of parallel multicast measurements. As depicted, minimizing drive test (MDT) information is provided from network node 115 to wireless device 110 in a first transmission 402. In certain embodiments, the MDT information may include configuration and scheduling information to be used by wireless devices 110 for the performance of parallel multicast measurements of MBMS transmissions. More specifically, in a particular embodiment, the first transmission 102 includes a MBMS control channel (MCCH) that is signaled to wireless device 110.
After wireless device 110 goes into an idle state 104, wireless device 110 may perform MDT measurements in accordance with the MDT information received in first transmission 102. In certain embodiments, the measurements may be performed in response to detection of an event that triggers the performance and logging of multicast measurements.
The performance of the parallel measurements may result in the generation of one or more MDT measurement log entries 106. The measurements may be logged and stored until wireless device 110 transitions into a radio resource control (RRC) connected state 108.
Upon transition to the RRC connected state 108, wireless device 110 may send a second transmission 110 to network node 115. The second transmission 110 may include radio resource control connection (RRCC) setup complete message and may include information identifying that MDT log information is available from wireless device 110.
In certain embodiments, network node 115 may respond to the second transmission 110 with a third transmission 112 that requests the MDT log information from wireless device 110. In response to third transmission 112, wireless device 110 may send MDT log information 114 to network node 115. Network node 115 may then save the MDT log information as trace records at state 116 and transmit the trace records to a trace collection entity in a fourth transmission 118.
The current version of 3GPP TS 36.133 specifies requirements for wireless device capabilities regarding event triggering and reporting criteria. The current requirements include mobility measurements and include a set of reporting criteria categories, a number of reporting criteria per category that a UE shall be able to support in parallel, and a maximum total number of reporting criteria. The current set of reporting criteria comprise three measurement categories used for mobility or positioning: intra-frequency, inter-frequency and inter-RAT measurements. As long as the measurement configuration does not exceed these requirements (e.g., different network nodes do not request from a wireless device more measurements than specified by the minimum requirement), the wireless device shall meet the performance requirements defined by the standard (e.g., all measurement accuracy and measurement time requirements that are relevant).
According to 3GPP TS 36.133, a reporting criterion corresponds to either one event (in the case of event based reporting), or one periodic reporting criterion (in case of periodic reporting), or one no-reporting criterion (in case of no-reporting, but when the wireless device is still expected to perform measurements).
A wireless device may be requested to make measurements under different measurement identities defined in 3GPP TS 36.331. Each measurement identity corresponds to either event based reporting, periodic reporting, or no reporting. For event based reporting, each instance of event, with the same or different event identities, is counted as a separate reporting criterion in the requirements for reporting criteria. For periodic reporting, a measurement identity is associated with one periodic reporting criterion. For no-reporting, a measurement identity is associated with one no-reporting criterion.
According to the current standards, a wireless device is able to support in parallel per category up to Ecat reporting criteria according to these requirements. For the measurement categories belonging to measurements on (a) E-UTRA intra-frequency cells, (b) E-UTRA inter-frequency cells, and (c) inter-RAT per supported RAT, the wireless device need not support more than the following total number of reporting criteria:                26 reporting criteria in total if the wireless device is not configured with any SCell carrier frequency,        35 reporting criteria in total if the wireless device is configured with one SCell carrier frequency and        44 reporting criteria in total if the wireless device is configured with two SCell carrier frequencies.        
Traditional measurement methods may include one or more disadvantages. For example, MDT logs may grow large in size. As one specific example, eMBMS measurements for 8 MBSFN areas and 15 MCHs per MBSFN area may result in up to 120 measurement sets, each set comprising corresponding MBSFN RSRP, MBSFN RSRQ, and MCH BLER measurements). This number of measurements may consume a large amount of wireless device resources. In addition, the wireless device may be performing other measurements, for MDT or other purposes (e.g., RRM, mobility, positioning, etc.). Particular advantages may be realized if total wireless device capacity can be efficiently shared among all the measurement procedures.
Another disadvantage may result when multiple network nodes configure a wireless device to perform different measurements for different purposes. If the network nodes are not aware of the wireless device's measurement capacity and the wireless device's currently configured measurements, the total amount of measurements requested from the wireless device at the same time may exceed the wireless device's measurement capacity.
Still another disadvantage may occur when measurements performed on broadcast signals, such as eMBMS measurements (MBSFN RSRP/MBSFN RSRQ/MCH BLER) may need to be performed in subframes with broadcast channels (e.g., MCH) scheduled. The MCH scheduling information determines, for example, the time needed to complete a measurement, the number of measurements that can be performed in the same subframes, and the frequency of the measurement samples.
The problems described above regarding a wireless device measurement capacity may also apply to the wireless device's measurement reporting capacity. Additionally, no wireless device measurements or reporting capabilities are currently defined that account for multicast or broadcast measurements. Furthermore, the same MDT logging configuration that is used to configure a wireless device for different measurements logging. Logging for legacy eMBMS, MDT, and MBSFN MDT measurements may not be configured simultaneously.